Welcome to Gaming SE Cat! To help us help you, can you provide some more details? For example, what have you tried doing? What specific parts of the game are you struggling with? Be as specific as possible in order to ensure a great answer.
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Jason BerkanFeb 17 '12 at 14:46

Please see the comment attached to Henry's answer. For this type of question it's best to explain why your solution is good, as well as possibly some pros/cons compared to other solutions.
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MBraedleyAug 27 '13 at 12:11

I managed to complete the level anyway even though my base was quite severely damaged in the process.

After the 3 Tesla coils, I built a goo gun to slow down the creeps, and then I had to build another Tesla coil (and later some missiles) near my base as some fast running creeps broke through anyway. I just used missiles and an AA gun to pass the level with the aircraft. I did not have to use any magic, and actually managed to pass the level.

As I got more money, I upgraded a few of my Tesla coils near the top left to BBQs as well as the one beside my base.

Have you tried creating a corridor near the base? I line up five towers in a line, south to north, then another line of four towers one space to the left, north to south, and a final line of two or three, as much as I can afford. With upgrade points, I'm putting out 13 towers at start. As you can, upgrade to the best mini guns, add some slow towers by round 10 or so, and get your AA when needed. Any time I have trouble with a level, it usually means I need to upgrade more.

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

Build some level 3 Tesla Coils where the creeps come, and it will defend you for a few early air waves too. That will help save money. Then build the air towers, and build some fart and goo towers to defend the ground waves, and if you have enough money building nukes will help too.